1. Field
The present invention relates to an adhesive composition for polarizing plates, a polarizing plate using the same, a method for preparing the same, and an optical member including the same.
2. Description of the Related Art
Adhesives for polarizing plates are used to attach a protective film to one or both sides of a polarizer including a PVA film. As such adhesives for polarizing plates, hydrophilic and water-soluble aqueous PVA adhesives are widely used in the art. However, a polarizing plate prepared using aqueous adhesives may suffer dimensional change due to heat from a backlight, casing localized screen distortion. As a result, partial light leakage can become significant in the case of allowing the overall screen to be displayed in a black state. Thus, the use of a cation polymerizable UV curing adhesive is proposed instead of the aqueous adhesives (For example, Japanese Patent Publication No. 2008-233874A, and the like).
However, since the cation polymerizable UV curing adhesive entails dark reaction (post-polymerization) after UV irradiation, a cured product of the adhesive can be easily wound during storage when prepared in the form of a wound roll. Moreover, the cation polymerizable UV curing adhesive is vulnerable to moisture in the course of curing, thereby making it difficult to maintain curing consistency. Thus, in order to obtain a uniformly cured state, it is necessary to strictly control not only surrounding moisture, but also the content of moisture in a PVA-based polarizer.
To fulfill operating conditions of the polarizing plate, there is a need for a polarizing plate that has better wet-heat resistance than typical polarizing plates in the art and includes an adhesive layer providing strong adhesion and high reliability, and outstanding cohesion, durability and waterproofing.